This invention relates to fasteners, and in particular to fasteners suitable for fixing into a wall or other panel by passing though an opening in the wall and extending a catch member to prevent subsequent withdrawal, when access is restricted to one side of the wall.
A number of fastener designs of this general kind are known. The present invention has one object to provide an improvement in such designs, and in certain embodiments to provide a fastener which can withstand large withdrawal forces without damage, and also to provide a fastener which can be withdrawn even when there is no access to the catch mechanism.
Generally, this invention is concerned with a fastener comprising a shank for extending through an opening from a near side to a far side of a wall and a catch retained in the shank of the fastener, in which the catch has first and second orientations in which, respectively, it projects less and more beyond the profile of the shank, whereby the catch can pass through a suitably sized opening in the first orientation but the catch engages the far side of the wall and prevents withdrawal of the shank from the opening in the second orientation. Means are suitably provided for tensioning the shank in the opening by reaction against the near side of the wall.
In certain embodiments of the invention, the catch may be adapted to swivel from the first orientation to the second orientation, and/or from the second orientation to the first orientation, by means of gravity. In some embodiments of the invention, the catch may rely on the sides of the opening to retain it in the first orientation while the shank is inserted in through the opening. In some embodiments, it may not be possible to return the catch from the second orientation to the first orientation, but, especially in cases where the fastener is not being inserted vertically through an opening, the catch may be arranged to swivel under the action of gravity when the shank is rotated in the opening, according to the rotary position of the shank.
In a preferred embodiment, the catch may comprise a retaining arm mounted in the shank of the fastener, movable between a first orientation in which it lies substantially wholly within the profile of the shank, and a second orientation in which it extends beyond the profile of the shank, whereby it can engage the far side of the wall when the fastener is subjected to tension forces tending to withdraw it from the opening.
In particular preferred embodiments of the invention, the shank is provided with an abutment supporting the catch in its second orientation.
The shank may be provided with a slot extending diametrically through the shank. The arm may be swivel mounted on a pin extending across the slot. The aforesaid abutment may be formed by a shoulder at one end of the slot.
The catch may be adapted to pivot on an axis that is offset from its centre of gravity. In certain embodiments, intended for fixing the fastener with its shank vertical, the centre of gravity of the catch is offset from the pivot axis in a direction radially outwardly of the longitudinal axis of the shank when the catch is in its first orientation, contained within the profile of the vertical shank, so that gravity tends to turn the catch and swivel it into its second orientation. In other embodiments, intended for use with the shank horizontal, the centre of gravity of the catch may be displaced from its pivot axis in a direction parallel to the longitudinal axis of the shank, so that gravity tends to swivel the catch into its second orientation when the fastener is inserted horizontally through an opening. The centre of gravity may be offset both axially and radially of the shank to enable the fastener to be used in a variety of orientations, and in particular also to enable the catch to be switched between the first and second orientations by rotating the fastener on its longitudinal axis.
The movement of the retaining arm is desirably restricted by abutments or other means in order to permit it to swivel from the first orientation to the second orientation in one direction only, and/or to swivel from the second to the first orientation in one direction only, normally the opposite direction. By limiting the freedom of the swivel arm to rotate, it can more easily be controlled.
The tensioning means may comprise nut means in screw threaded engagement with the shank. Other means having equivalent effect may equally be used.
The fastener may be provided with marking whereby the orientation of the shank may be indicated, even when the part of the shank holding the catch is invisibly contained in or beyond the opening, so that a user can more conveniently control the orientation of a gravity operated catch by appropriately turning the fastener in the opening. Such marking may be on an end of the shank directed, in use, towards the near side of the wall.